Wafer alignment device and method

Abstract

An alignment target structure includes a reflective member and a non-reflective field proximate to the member. The field is configured to enhance identification of the target and/or to enhance contrast between the member and the field. The field may include an absorptive structure and/or a diffractive structure.

What is claimed is:  
     
         1 . An alignment target comprising: 
 a reflective member; and    a non-reflective field configured to be proximate to said reflective member and comprising an absorptive material and a scattering structure, wherein said absorptive material comprises a poly-crystalline material.    
     
     
         2 . The alignment target of  claim 1  wherein said scattering structure comprises at least one edge slope.  
     
     
         3 . The alignment target of  claim 2  wherein said at least one edge slope is formed by boundaries between areas of poly and no poly.  
     
     
         4 . The alignment target of  claim 3  wherein said edge slopes are created in a checkerboard pattern.  
     
     
         5 . The alignment target of  claim 4  wherein said reflective member comprises a metal.  
     
     
         6 . The alignment target of  claim 2  wherein said at least one edge slope is formed by contact cuts in a single material.  
     
     
         7 . The alignment target of  claim 2  wherein said edge slopes are formed by diffusion.  
     
     
         8 . The alignment target of  claim 2  wherein said edge slopes are formed on more than one layer.  
     
     
         9 . The alignment target of  claim 5  wherein said reflective member comprises two rectangular reflective members located at right angles to each other.  
     
     
         10 . An alignment target comprising: 
 a reflective member; and    a non-reflective field configured to be proximate to said reflective member and comprising at least one of an absorptive material and a scattering structure.    
     
     
         11 . The alignment target of  claim 10 , said non-reflective field comprising both said absorptive material and said scattering structure.  
     
     
         12 . The alignment target of  claim 10  wherein said absorptive material comprises a poly-crystalline material.  
     
     
         13 . The alignment target of  claim 10  wherein said scattering structure comprises at least one edge slope.  
     
     
         14 . The alignment target of  claim 13  wherein said at least one edge slope is formed by boundaries between areas of poly and no poly.  
     
     
         15 . The alignment target of  claim 14  wherein said edge slopes are created in a checkerboard pattern.  
     
     
         16 . The alignment target of  claim 15  wherein said member comprises a metal.  
     
     
         17 . The alignment target of  claim 13  wherein said at least one edge slope is formed by contact cuts in a single material.  
     
     
         18 . A wafer alignment system comprising: 
 a photo-detector;    a wafer configured to be scanned by a beam from said photo-detector; wherein said wafer comprises an alignment target further comprising: 
 a reflective member; and  
 a non-reflective field configured to be proximate to said reflective member and comprising at least one of an absorptive material and a scattering structure, wherein said non-reflective field is configured to enhance contrast in the amount of said beam reflected to said photo-detector by said non-reflective field and said reflective member and thereby enhance wafer alignment.  
   
     
     
         19 . The wafer alignment system of  claim 18 , said non-reflective field comprising both said absorptive material and said scattering structure.  
     
     
         20 . The wafer alignment system of  claim 18  wherein said absorptive material comprises a poly-crystalline material.  
     
     
         21 . The wafer alignment system of  claim 18  wherein said scattering structure comprises at least one edge slope.  
     
     
         22 . The wafer alignment system of  claim 21  wherein said at least one edge slope is formed by boundaries between areas of poly and no poly.  
     
     
         23 . The wafer alignment system of  claim 22  wherein said edge slopes are created in a checkerboard pattern.  
     
     
         24 . The wafer alignment system of  claim 23  wherein said member comprises a metal.  
     
     
         25 . A method of aligning a wafer comprising the steps of: 
 shining a beam of light from a light source onto a wafer;    reflecting a portion of said beam of light from a reflective member to a photo-detector;    reflecting a reduced portion of said beam of light from a non-reflective field to said photo-detector, wherein said reflecting a reduced portion step comprises at least one of the steps of: absorbing a portion of said beam of light and reflecting a portion of said beam of light away from said photo-detector;    identifying a current position of said wafer based on the contrast in said beam of light reflected from said reflective member and said non-reflective field; and    adjusting the position of said wafer based on said current position of said wafer.    
     
     
         26 . The method of  claim 25 , wherein said reflecting a reduced portion step comprises the steps of: absorbing a portion of said beam of light and reflecting a portion of said beam of light away from said photo-detector.  
     
     
         27 . The method of  claim 25  wherein said absorbing step is facilitated by a poly-crystalline material.  
     
     
         28 . The method of  claim 25  wherein said step of reflecting a portion of said beam of light away from said photo-detector includes scattering said beam of light with at least one edge slope.  
     
     
         29 . The method of  claim 28  wherein said at least one edge slope is formed by boundaries between areas of poly and no poly.  
     
     
         30 . The method of  claim 29  wherein said absorbing and said scattering are caused by edge slopes created in a checkerboard pattern with said poly and no poly areas.